The present invention relates to a blood flow meter for measuring blood flow on the surface of a test area by attaching a probe with plural thermocouples in series onto the test area, and also to measurement of skin blood flow with the flow meter.
An example of the system for measuring skin blood flow has been proposed by A. V. J. Challoner (`Accurate measurement of skin blood flow by a thermal conductance method`; Medical and Biological Engineering, pp 196-201; March 1975). The system includes a pair of probes with plural thermocouples and a power circuit for supplying a constant current to a heated disc of each probe. One of the probes is placed on a control or untreated site of the skin while the other on a test or treated site, and the blood flow of the test site is expressed as a difference in the thermo-EMF (electromotive force) or ratio of the readings from the two probes.
The prior system, however, can only show the blood flow on a test site as a relative value, that is, a ratio of the thermo-EMF determined by dividing the control reading by the test reading, and does not express the flow as an absolute value. Cutaneous blood flow affects the temperature of the heated disc as well as a heat-sensitive ring and varies the reference temperature of the disc, which is supposed to be constant, thus causing errors in the relationship between the thermo-EMF and the blood flow. The system also requires two probes which are attached to the test site and the control site.